Half thrust bearing for crankshaft of internal combustion engine

Abstract

A half thrust bearing for a crankshaft includes a back metal layer defining a first surface and a second surface, and a bearing alloy layer on the first surface to form a slide surface, and thrust relieves formed adjacent to both circumferential end surfaces and having a thrust relief surface consisting of the bearing alloy layer. Each circumferential end surface of the back metal layer includes an exposed end surface adjacent to the second surface, and a transition surface adjacent to the first surface. The bearing alloy layer further includes an extension portion covering the transition surface and having extension end surface adjacent to the exposed end surface, the extension end surface and the exposed end surface extending at least partly in the same plane.

The invention claimed is: 
     
       1. A semi-annularly shaped half thrust bearing for receiving axial force of a crankshaft of an internal combustion engine, the half thrust bearing comprising a back metal layer made of an Fe alloy that defines a first surface and a second surface on a side opposite to the first surface, and a bearing alloy layer provided on the first surface of the back metal layer, the bearing alloy layer comprising a slide surface on a side opposite to the back metal layer, the half thrust bearing further comprising two thrust reliefs formed adjacent to both circumferential end surfaces of the half thrust bearing, each thrust relief comprising a thrust relief surface formed so that a wall thickness of the half thrust bearing becomes smaller from the slide surface toward the circumferential end surface, wherein
 the thrust relief surface consists of the bearing alloy layer, 
 in the thrust relief, the back metal layer is formed so that a thickness thereof becomes smaller toward the circumferential end surface, 
 each circumferential end surface of the back metal layer comprises an exposed end surface adjacent to the second surface that configures a part of the circumferential end surface of the half thrust bearing, and a transition surface formed between the first surface and the exposed end surface, and 
 the bearing alloy layer further comprises an extension portion extending toward the second surface of the back metal layer so as to cover the transition surface, wherein the extension portion comprises an extension end surface configuring a part of the circumferential end surface of the half thrust bearing, the extension end surface being formed adjacent to the exposed end surface, so that the extension end surface and the exposed end surface extend at least partly in the same plane. 
 
     
     
       2. The half thrust bearing according to  claim 1 , wherein an axial length (A 1 ) of the extension portion in the circumferential end surface of the half thrust bearing is 0.2 to 1.5 mm. 
     
     
       3. The half thrust bearing according to  claim 1 , wherein an axial depth (RD 1 ) of the thrust relief from the slide surface in the circumferential end surface of the half thrust bearing is constant between a radially inner end and a radially outer end of the half thrust bearing, and 0.1 to 1 mm. 
     
     
       4. The half thrust bearing according to  claim 1 , wherein a length (L 1 ) of the thrust relief from the circumferential end surface of the half thrust bearing is constant between a radially inner end and a radially outer end of the half thrust bearing, and 3 to 25 mm. 
     
     
       5. The half thrust bearing according to  claim 1 , wherein at least the slide surface of the bearing alloy layer is covered by an overlay layer.